Apparatus for use in electric telegraph systems



May 22, 1928.

F. .G. CREED ET AL APPARATUS FOR USE IN ELECTRIC TELEGRAPH SYSTEMS FiledMay 24, 1924 Patented May 22, 1928.

FREDERICK GEORGE CREEDIAKND ETHELRED ALFRED WILLSON, or CROYDON,ENGLAND.

ArP nATU's FOR use In ELECTRIC TELEGRAPH sy mns.

' Application filed may 24, 1924, Serial no. 715,636, and in GreatBritain Jim 11, 1923. v

This invention has reference to improvements in quadruplex and diplextelegraph systems which provide for the simultaneous transmission ofsignals in opposite directions, without interference, o'ver asing'letelegraph line. i

Quadruplex telegraph systemsare generally based on a combinatiomat eachstation, of the single-current and double-cur-j rent duplex systems.Such'systems may be worked according to the differential or bridgemethod. The single current duplex system permits of the simultaneoustransmission of one message in each direction through changes in currentintensity, and the double current system, permits of thesimultaneoustransmission of one message in each direction throughchanges in current direction. The latter transmission is effected onwhat is called the A side and the former on whatis called the B side-ofthe combined apparatus used for effecting such simultaneoustransmission. Each station is provided with two current transmittingkeys and two ditii'erent-ially wound receiving i elays, one key,arranged on the A side of the combined apparatus employed, and usuallycalled the reversing key, bei g adapted to reverse the direction of thecurrent"'sei1t t-hereby to line without altering its strength, and the18d apparatus, and usually called the inment key, being adapted tochange the strength ofthe current sent thereby to hn'e without alteringits direction, whilst of the two relays, one is a polarized relayarranged on the A side and adapted to control tele' graph receivingappr"at'tis on that side,

whilst the other relay is anon-polarized're lay arranged on the B sideandadapted to side of the respective stations and to use the receivedsignals for, automatically operating, at high speed, telegraphic receivng apparatus, for instance apparatus of the kind known as the Creedreceiver,whiel1' perforates a tape, messages of signals can only betransmitted and received on the B side of the respective statio'nsat acom paratively slow rate of speed such that they have to he transmittedhand operated o her key, arranged on the B sideof the com keym'echanismand when received, have to be translated by telegraph operators with theaid of a Morse sounder or printer.

This is in part due to the fact that if, during the time that thecurrent increment key on the B side of one station is depressed toincrease. the current strength, the current from the marking contactscrew of the relay, thereby causing a break in the B side signals. Thisaction" is known amongst telegraphists as the B kick.

Although means have heretofore been adopt-ed with a view to avoidingthis dis advantage, such means require frequent adjustment and havenever been such as to en able messages to be transmitted and received onthe B side of the transmitting and receiving apparatus at high speedlike those on the A side of theapparatus.

N ow the'pre'sent invention has for its ob-' jeet to provide apparatusfor use in a quad rnplex telegraph system of the kind referred to, 'orin a diplen telegraph system,means whereby the transmission of signalson the B. side of each station can be effected as rapidily as those onthe A side, and also means to enable the signals received on the B sideof each station to be utilized'in an effective manner, for the automaticoperation of receiving apparatus, as for instance a. Creed receiver, inthe same way that the signals received on the A side of each station canbe used for this purpose, and thus to enable; the whole of thequadruplex or diplex telegraph system tobe operated at high speed and inan automatic manner, so as thereby to increase the capacity of the wholesystem forquickly dealing with telegraphic work. Q

In the accompanying illustrative draw-v ings, Fig. 1 shows,diagrammatically, an arrangement of apparatus suitable for use ina'quadruplex telegraph system and whereby the object of the inventioncan be'attained. Fig; Q'sh'ows, diagrammatically,- a modifiedtransmitter.

In the arrangement shown in Fig. 1, there is provided on the A side ofeach of two connected stations, a current reversing key comprising amovable contact lever 1 mounted between stationary and movable contactsa and b and acted upon by a spring (Z that tends. to move it towards andagainst the stationary contact a. The movable contact b is carried bythe tongue 6 of a powerful high speed polarized relay E worked from ahigh speed transmitter of the VVheatstone or other desired type,indicated diagrammatically at H. The stationary and movable contacts aand b are connected to the current increment key mechanism at the samestation, as hereinafter described. The spring controlled contact lever 1is connected to line f and to the artificial line 7, through conductorsg, a polarized relay C and a non-polarized relay D provided at the samestation, for receiving signals transmitted from the second station,which is similarly equipped. The two relays C and D are constructed andcoupled up to the lines 7 and f in the usual manner but the movabletongue h of relay D is arranged to work between two contacts 2' and j,as and for the purpose hereinafter described.

The key mechanism on the B side of each station, used for varying thestrength of the current signals, comprises two movable spring controlledcontact levers 2 and 3, one

of which, namely 2, is arranged to work between stationary and movablecontacts and p respectively and the other of which, namely 3, isarranged to work between other stationary and movable contacts 1" and 8respectively. Contact a is connected through a conductor a to lever 3,and contact I) is.

connected through a conductor to lever 2. Contact 0 is connected througha conductor 0 and a resistance 0 to. an intermediate point m or theelectric battery m, such that one third part of the battery is includedbetween such point and one pole m say the positive pole, of the batterywhich is connected to earth t. Contact 2) is connected through aconductor p and a resistance p to the opposite or negative pole m of thebattery we so that the whole of the battery is included between it andearth. Contact a is connected through a conductor 1 and a resistance rto one pole at, say the positive pole, of the second battery n, theopposite or negative pole n of which is connected to earth 75. Contact 8is connected through a conductor 8 and a resistance 8 to a point n inthe second battery n, such that a third part of the battery is includedbetween such point and the negative pole n of the battery. The twobatteries m and a may, as shown, have a common earthed terminal tContacts p and s are insulated from each other and carried by the tongueat of another powerful high speed polarized relay F of the two batteriesm and n,

which is worked from another high speed transmitter of the Wheatstone orother desired type, indicated diagrammatically at l. The arrangement issuch that. assuming. lever 2 to be hearing, under the action of itsspring w, against contact 0 and that the tongue at of relay F is, asshown, in its ex treme right hand position away from said lever, then,upon the tongue moving tofthe left, contact p carried thereby willimmediately act against lever 2 so as momentarily to short circuit theleft hand portion of the associated battery m and then move le'ver2,against the action of its spring w, from contact 0 and will remain incontact with such lever during the further left hand motion of thetongue and also during the right hand motionthereof until lever 2 isagain caused, by its spring, to bear against contact 0. On this furthermovement of the tongue to the right, contact .9 will act against lever23, momentarily short 'circuiting the right hand portion of theassociated battery it and then immediately move such lever 3 fromcontact 7" and will, under the action of the spring m connected to lever3, continue to bear against'that lever during the remainder of themovement of the tongue to the right and also during the movement of thetongue to the left until lever 3 again bears against contact 7' when theconnection between contact s andlever 3 will be opened.

The use of contact levers such as 1, 2 and 3, arranged and actuated asdescribed, constitute an important feature of the present invention.

The arrangement is also such that assum ing contact lever 1 is held byits spring in contact with the stationary contact a and that the tongue6 of the polarized relay E carrying contact I) is bearing against itsback stop is, then, immediately the tongue, on its forward movement,acts upon the contact lever 1 through its movable contact 6, theportions of the batteries m and n between the points m and a or thewhole according to the position of the levers 2 and 3, will momentarilybe short circuited and the lever 1- caused tobreak connection withcontact a. The connection between contact I; and contact lever 1 ismaintained during the further forward movement of the tongue and also,owing to the action of the spring d, during the backward movement of thetongue until the contact lever, under the said action of the spring,again bears on the contact a, whereupon the connection between themovable contact I) and lever 1 will be broken. V

The short circuit current produced as described, is limited. in eachcase, to a safe value by the resistances 0 and 8 or 72 and r in therespective circuits, these resistances being of suitable value for thepurpose.

Hit;

The resistances 0 and s arethose normally used for maintaining theduplex balance when the batteries are, during operation of the incrementkey mechanism, reduced to one third of their maximum value.

By means of the hereinbefore described Consequently, the time betweenthe fall of current from a working value of one polarity and the rise ofcurrent to a similar value of the opposite polaritywill be considerablyreduced as compared with that obtaining with known quadruplex telegraphsystems of the kindherein referred to. As a result, the B kickheretofore experienced in such system is very considerably reducedthough not entirely eliminated. Means are however provided at thereceiving end of the line to entirely eliminate the effect of the B kickas hereinafter described.

To enable the signals transmitted as described at a high rate of speedfrom the B side of the quadruplex apparatus at one station to bereceived .and'efi'ectively utilized by the telegraphic receiver .at theB side of the quadruplex apparatus at a second station and so asentirely to eliminate the effect of the B kick referred to, there isassociated with the non-polarized relay 'D at that station through whichthe quadruplex telegraphic signals or messages pass as heretofore, ahigh speed polarized relay G. This relay is adapted to be actuated bycurrents derived from a local battery 4 under'the control of the movabletongue h of thenonpolarized relay D and the two stationary contacts 2'and of that relay between which the tongue moves and which are.connected to the opposite poles'of the said battery 4;

One terminal 5 of relay G is connected to the tongue h of the relay Dand the second terminal 6 of relay G is connected to the middle point 4'of the-said local battery '4. The movable tongue 7 of relay G isconnected to one terminal 8 of a circuit including a high speedtelegraphic receiver 9 on the B side of the quadruplex'apparatus andworks between two stationary contacts 10 and 11 connected to theopposite terminals of a second local battery 12 which may, as in theexample shown, be that provided on the A side of the'apparatus forworking, in known manner, the high speed telegraphic receiver 13 on thatside. under the control of relay C. 14 are resistances" arranged inknown manner in the circuits leading to the telegraphic receiver 13,and14' are similar resistances arranged in the circuits leading to thetelegraphic receiver 9.

The signals as received in the non-polarized relay D at one station willstill :be re-. ceived broken while thereversing key on the A side at theother station is being operated but the breaksswill be small and not ofsufficient duration to allow the tongue h of the said-relay D to moveover to the spacing contact 2' of the relay but merely to cause thetongue to tremble. Relay Gr being connected up as hereinbeforedescribed, it will be seen that its tongue 7 will not be moved to thespacing side of that relay unless the tongue h of relay D makes definitecontact with the spacing contact 2' of that relay. This entirelyeliminates the effect of the reduced B kick. Thus, by the meansdescribed, the high speed signals sent, as hereinbefore described, fromthe B side of the quadruplex apparatus at one station and designed to bedealt with by relay D at a second station, can be accurately reproducedat a high speed by relay G and utilized for operating, in an effectivemanner, the high speed telegraphic receiver 9 on the B side of theapparatus at the second station.

The high speed polarized relays E, F and G, may advantageously be of thekind described in the specification of application for Letters Patent,Serial No. 497,459, or of the kind described in the specification ofanother application for British Letters Pat.- ent dated. 11th March,1924, and numbered 6,214. It is important that the polarized relay Gshould be so constructed that firm contact pressure is maintainedbetween the moving contact and one or otherof the stationary contactseven though the current in the relay coil or coils falls to zero, at anytime, the tongue not moving to the opposite contact until the current isactually reversed. This condition is complied with in polarized relaysof the kind referred to. The telegraphic receivers 13 and 9 on the A andB side of the quadruplex apparatus in each station may advantageously beof .the automatic type knownas Creed receivers, hereinbefore referredto, but other kinds of automatic receivers operated by transmittedcurrents can be used.

From the foregoing description of quadruplex apparatus, it will beunderstood that, in the arrangement described, there are employed interalia at each of two connected stations, current reversing key mechanismand current increment key mechanism, of the special constructiondescribed. arranged respectively at the A and B sides of the station,each of these key mechanisms being operated by the movable member ortongue of a high speedpolarized relay, the two relays being workedby'twohigh speed transmitters of the \Vheatstone or other desired type.'Also, as above indicated, two autoizo matic high speed receivingapparatus 13 and 9 are arranged at the A and B sides respectively ofeach station together with associated relays C, D and G to receive andutilize the two sets of signals transmitted from the opposite station.

In the case however of telegraph systems in which it is only desired totransmit two messages simultaneously at a high speed along one line wirefrom one station to another station and to transmit a n'iessagesimultaneously along the same wire from the second station to the firstone at hand speed, that is to say, when working on, the diplex system,it will of course only be necessary to employ high speed currentreversing key mechanism and current .increment key mechanism withassociated automatic high speed transmitters at the transmittingstation, and only two sets of high speed receiving apparatus at thesecond or receiving station with associated relays C, D and G. For thehand speed messages, it will of course be necessary to supply a Morsekey at the one station, and a sounder or Morse inker at the otherstation.

Instead 01 causing each VVheatstone or.

other transmitter to operate the contact lever 1, or contact levers 2and 3, ot the respective key mechanisms by the aid or" a high speedpolarized relay E or F as hereinbetore described, each lever may beoperated mechanically from the transmitter. Fig. 2 shows,diagrammatically, one arrangement for this purp In this example, 15 isthe tape teed wheel, 16, 16 the peckers, 17, 17"v the spring controlledbell crank levers connected to the peckers and 18 the rocker beam,actuated by a driving shaft, of an ordinary construction of Wheatstonetransmitter. 20 is a lever that is oscillated about an axis at 21through connections 22 and 28 from the levers 17 and 17, and 2a is aspring pressed ockey pulley that acts on one end of the lever20 toensure a smart and decided action of the lever 20 in the same way thatthe contact lever used in a VVheatstone transmitter is controlled. Thelever 20 is provided with an arm 25 having a bifurcated end 25 whichconstitutes one member of an escapement device the other member of whichis constituted by a disc 26 having a tooth 26* adapted to co-actalternately with the two prongs ot the bifurcated memmer 25 Theescapement member 26 is fined upon a spindle 27 driven through afriction clutch 28 from a shaft 29 that is driven at a Suitable speedfrom the driving shaft used for driving the rocker beam 18, feed wheel15 and associated parts. On the spindle 27 is an eccentric 80, the rod31 of which is arranged to operate a lever 32 which is pivoted at 32 andwhich takes the place of the tongue 6 used for operating the lever 1 ofthe current reversing key mechanism, or the tongue 10 used for operatingthe levers 2 and 3, of the current incrementkey mechanism used in theapparatus shown in Fig. 1. Inthe example shown, the lever 32 is shown asarranged to operate the levers 2 and 3 of the current increment keymechanism. As will be seen, at each operation of the transmitter, theescapement Will act to release thespindle 27 and permit it torotatethrough half a revolution and through the eccentric Y30 and rod31, movethe lever 32 in one direction or the other.

Quadruple); and 'diplex telegraph systems, according to the invention,embody, of course, resistances, condensers, galvanometers and soforth,such as are commonly used in such systems for well known purposes.

In quadruplex and dipleX telegraph systems, provided with highspeedsignal transmitting and receiving apparatus of the kind referredto, it is important, in order to obtain the best results in working ofthe com bined apparatus, that the start-ing of a dot signal by both thecurrent reversing key mechanism on the A side and the current incrementkey mechanism on the. B, Side, should take place simultaneously and thatthe stopping of the said dot signals by both sets of mechanism shouldtake place simultaneously, in order that-the current impulses producedby the two key mechanisms shall be accurately superimposed upon oneanother and be transmitted at the same time, that is to say,thatthey'should be in phase with one another, and not follow oneanother, which would cause splitting of the current signal of increasedstrength, and interference withthe proper transmission, re-

ception and utilization of the respective impulses. To this end, the dotsignals are pro-.

duced simultaneouslyby the two key mechanisms, accurately in phase withone another, by driving the two high speed Wheatstone or othertransmitters H and I used at each of two connected stations, in aquadruplex system, or at one station in a diplex telegraph system,according to the present invention, at the same speed, or at suchrelative speed, that the dot signals produced by the two transmittersand transmitted to line shallaccurately be in phase with one an other.Consequently, the starting of. a current impulse by the currentreversing key mechanism, under the control 01 the high speed transmitterH, to produce adot signal in the line wire, and the starting of acurrentimpulse of increased strength by the increment key mechanism, under thecontrol of its high speed transmitter I, also to produce a dot signal inthe line wire, will be caused to take place simultaneously, as also willthe stopping of the two current impulses, the two current impulses beingthus in phase.

In this way,.splitting of the last mentioned or increased currentimpulse, whentransmitting a dot, can be avoided. When a dash is beingtransmitted on theB side, the B kick Will occur, if dots are beingtransmitted on the A side, but the .dash'is not curtailed'in length, asit starts and finishes in phase with the dot signals.

Two high speed Wheatstone or other transmitters combined with a singlemotor, or-

driving means common to them, and suitable for use in telegraph systemsgenerally wherein it is desired simultaneously to transmit two sets ofsignals in'the same direction and in phase, along a single line Wire,from one station, or from each of two stations, forms the subject of aseparate application for British'Letters Patent'filed byus, dated 4thJuly 1923 and numbered 173%. As will be obvious, decrement key mechanismmay be used instead of increment key mechanism. Such decrement keymechanism is to be understood'as the alternative of increment keymechanism and both kinds .of such mechanism are to be I understoodasincluded in the term current five or other multiple unit systems andstart;

augmenting mechanism used in the appended claims,

The details of construction of apparatus embodying the present inventionmay be modified Without departing'irom the essen 30- V tial feature ofthe invention.

Quadruplex and diplex telegraph apparatus embodying the invention can beused not only for signalling by the Morseland line code but it can alsobe used for transmit ting and receiving signalsaccording to the and stopsystems. :Also, insteado'f using the apparatus to form a single channelsystem as hereindescribed, several sets 'of such apparatus may be usedto constitute a multiple channel system.

What we claim is 1. In a telegraph system comprising a transmittingstation, a receiving station and a line circuit between said stations,means adapted simultaneously to transmit reversed currents and augmentedcurrents through transmitting station and a receiving-station,

said line circuit, each reversed current impulse, representing a dot,and each augmented currentimpulse, representing a dot, startingsimultaneously and stopping simultaneously, so that the tWo impulseswill be accurately in phase with one another.

2. In a telegraph system comprising a transmitting station, a: receivingstation and a line circuit between said stations, means located at thetransmitting 'stationadapted simultaneously to transmit reversedcurrents and augumented currents through said line circuit, eachreversed current impulse, representinga dot, and each augmented currentimpulse representing a dot, starting simul-' taneously and stopplngsimultaneously, so

that the two impulses Will be accurately in phase with one another, andreceiving means located at said receiving station comprising apolarize'd relay and a non-polarized relay and separate automaticreceiving devices controlled by the respective relays.

3. In a telegraph system comprising a transmitting station and areceiving stabeing transmitted simultaneously, each reversed currentimpulse, representing a-dot and each augmented current impulserepresenting a dot, Will start simultaneously and Will stopsimultaneously so that the two impulses will accurately be in phasewithone another.

I 4. In a telegraph system comprising a transmitting station and areceiving station, a line circuit connecting said stations,

current reversing means and current augmented' means arranged at the Aand B sides respectively of the transmitting station for transmittingtwo sets of signals simultaneously tosaid line circuit, two telegraphictransmitters adapted toactuate said current reversing means and currentaugmenting means inunison so that each reversed current impulse,representing a dot, and each augmented current impulse, representing a'dot,w'ill start simultaneously and Will stop simultaneously sot-hat thetwo impulses Will accurately be in phasewith'one another, signalreceivingdevices arranged at the A and'B sides of the receivingstation,-

and automatic receiving apparatus, also arranged at the A and B sides ofthe receiving station and respectively controlled bythe signal receivingdevices at thecorresponding sides of the receiving station.

5. In a telegraph system comprising a a line circuit-connecting saidstations, means adapted to transmit current of reversed sign and alsomeans for transmitting currents of augmented strength, simultaneously tosaid line circuit and located at the A and B sides respectively of thetransmitting station andtwo telegraphic transmitters adapted to causethe two current transmitting I will stop simultaneously sothat the two.im

pulses will'accurately be in phase With, one another, a polarized'relayand a non-polarized relay arranged the-line circuit and v at the Aand B sides respectively of the receiving station and separate automaticre ceiving devices controlled by the respective relays.

6. In a telegraph system comprising two stations and a line circuitbetween said stations, current reversing key mechanism and currentaugmenting key mechanism arranged at one station and adapted to transmittwo sets of signals simultaneously to said line circuit, said currentreversing key, mechanism comprising a stationary contact, a movablecontact, said contacts being electrically connected'to the currentaugmenting key mechanism, a movable arm carrying said movable contact, acurrent reversing lever mounted to work between said stationary andmovable contacts and connected to said line circuit, a spring tending tomove said lever towards and against said stationary contact and atelegraphic transmitter adapted to oscillate said arm andcauseelectricsignals of alternately opposite sign to be :one pole toearth, said current reversing key I 1 transmitted to the line circuitunder the control of the transmitter. v I

7. In a telegraph system comprising two stations and a line circuitbetween said stations, current reversing key mechanism and currentaugmenting key mechanism arranged at onevstation and adapted to trans-'mit two, sets of signals simultaneously to said line circuit, twobatteries common to the two key mechanlsms and connected at mechanismcomprising a stationary contact, a movable contact, an arm carrying saidmovable contact, a current reversing lever mounted to work between saidstationary and movable contacts and connected to said line circuit and aspring tending to move said lever towards and against said stationarycontact, and said'current augmenting key mechanism comprising twoseparate levers, a stationary contact and a movable contact associatedwith each of the two last mentioned levers, a spring associated witheach of said two levers and tending to move the corresponding leveragainst the corresponding stationary contact, a second movable armarranged between the said two levers and carrying at opposite sidesthereof the two movable contacts associated with the said two levers,one of the said two levers bein connected to the movable contact of thecurrent reversing keymechanism and the other of the two said leversbeing connected to thestationary contact of the said current reversingkey mechanism and the stationaryand movable contacts associe ated withthe said two levers being insulated from each other and connectedsubstantially as herein described'to said electric batteries, andtelegraphic transmitters adapted to work in unison with one another, onetransmitter being arranged to cause the oscillation of the lever of thereversing key mechanism andthe other to cause the oscillation of the-twolevers of the current augmenting key mechanism, substantially asdescribed.

8. A telegraph system comprising two stations and a line circuit betweenthem, current reversing mechanism and current. augmenting mechainismlocated at one station and associated with the line circuit, separaterelays associated with the current, reversing mechanism and currentaugmenting mechanism and adapted to operate the. same and separatetelegraphic transmitters adapted to operate said relays and therebyenable two sets of signals to be transmitted simul taneously to the linecircuit, said transmitters being driven in unison so that each reversedcurrent impulse, representing a dot, and each augmented current impulse,representing a dot, will startsimultaneously' and .will stopsimultaneously so that the two impulses will accurately be in phase withone another. c v

9. A telegraph system comprising two stations and a line circuit betweenthem,

current reversing means and current augmenting means located at the Aand B sides of one station and adapted simultaneously to transmit to theline circuit two sets of signals, each reversed currentimpulse,*representing adot, and each augmented cur-- rent impulse,representing a dot, starting simultaneously and stopping simultaneously,so that the two impulses will be accurately in phase with oneanothe'r,'a polarized relay .and a non-polarized relay arranged at the Aand B sides respectivelylof the other station and in the line circuitand automatic high speed receivingv devices arranged at the A and Bsides of the second station and separatelycontrolled by the relays atthe corresponding'sideslof the station.

10. A telegraph system, comprising two stationsand a line circuitbetween them,

current reversing means and current aug menting means located at the Aand B sides of one station and adapted to transmit simultaneously to theline circuit two sets of signals, each reversed current impulse,representing a dot, and each augmented current impulse, representing adot, starting simultaneously andistopping simultaneously, so that thetwo impulses will be accurately in phase with one another, apolarizedrelay and a non-polarized relay arranged at the A and Bfsi desrespectively of theother station and in the line circuit, an

current fromsaid local battery under the" control of the non-polarizedrelay and an automatic high. speed receiving device arranged at the Arent impulse, representing a dot, starting,

simultaneously and stopping simultaneously, so that the two impulseswill be accurately in phase with one another, a polarized relay and anon-polarized relay arranged in series with each other and with saidline circuit at each station and two high speed receiving deviceslocated at each station, one controlled by the polarized relay and theother by the non-polarized relay at the corresponding station.

12. A quadruplex telegraph system comprising two stations, a linecircuit between said stations, current reversing means and currentaugmenting means located at the A and B side of each station adapted totransmit simultaneously to said line circuit reversed currents andaugmented currents, each reversed current impulse, representing a dot,and each augmented current impulse, representing a dot, startingsimultaneously and stopping simultaneously, so that the two impulseswill be accurately in phase with one another, a polarized relay andnon-polarized relay arranged at the A and B sides respectively of eachstation and in series with one another and the line circuit, a localbattery at each station, a high speed polarized relay at the B side ofeach station, energized by current from the local battery at thecorresponding station under the control of the non-polarized relay atthe same station, and two high speed automatic receiving devices at eachstation, one receiving device being controlled by the polarized relay'atthe A side of the corresponding station and the other controlled by thehigh speed polarized relay at the B side of the corresponding station.

Signed at London, England, this twelfth day of May 1924.

FREDERICK GEORGE oREEn.

ETHELRED ALFRED WILLSON.

